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I switched of the main circuit breaker to the house and opened up a light switch to see if I had a neutral wire, so I could buy a smart switch.

two-switch junction box

But when I took off the plate I found what appears to be a #14/2 wire hiding there in the back of the metal junction box-- just snipped off, with the hot, neutral, and ground wire exposed!

exposed wiring

Is my family or my house in danger? What should I do to these wires?

  • Do you have a multimeter (not a non-contact voltage detector) that you can probe those wires with? It's most likely an abandoned, unused wire, but based on the condition of the ground wire that I can see, a non-professional was working in that box. – JPhi1618 Jul 17 at 19:47
  • Also, because the switch on the right is a 3-way, that white wire might not be a neutral. And is one of the whites connected to the grounds? Oh, house and family are not in imminent danger, but you probably want to figure this out before doing anything else in this box (including putting the existing switches back). – JPhi1618 Jul 17 at 19:49
  • I do have a Klein NCVT-3, but I was under the impression that I should not have the wall plate disconnected or the switches pulled out if the breakers are on. How can I test those without A) putting myself in more danger or B) getting false positives from the wires attached to the switches? – Kerrick Jul 17 at 21:18
  • I will post an answer with more information, but you will need a multimeter with test leads. A non-contact voltage detector like you have isn't good for troubleshooting. It's only purpose is to make sure you're not about to get shocked. – JPhi1618 Jul 17 at 21:22
  • Welcome to the site - looking forward to the next question where you ask about what else is going on in that box. – JPhi1618 Jul 17 at 21:39
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First, this wire is probably dead and unused because of how short someone cut it. It's not usable like that and I would hope the person that cut it intended it to be dead and never used in the future. That said, the work was done by an amateur so you shouldn't assume anything.

You are correct that you shouldn't work on a circuit when the breaker is on (referring to a comment), but in order to troubleshoot some problems, and to measure voltage, the power must be on.

Move the switches out of the way as much as possible. If you want, you can even wrap electrical tape around the switches to cover up the screws and limit accidental contact. Turn the switches on and then turn on the breaker. Your mulitmeter will have probes that are 3-5" long, so you should be able to reach the back of that box while staying clear of the switches. Just assume that everything in the box can shock you and only touch wires with the insulated probes of the meter. (Ground and neutral should be safe, but we have no idea what's going on in this box, so assume it's all dangerous.)

Probe the black and white wires and then black and ground to see if there is any voltage present. They are probably, hopefully going to be dead. If they are dead, just leaving them alone is the easiest thing to do. They should be capped, but they've been cut so short, that's not possible. You could loosen the cable clamp, grab the wires with pliers and try to pull more into the box. If successful, cap the wires with wire nuts. If there is voltage on the wires, then the really need to be capped off.

Also, the voltage that you're looking for is close to 120vac. The meter can read phantom or induced voltage on dead wires that run along side live wires. Your non-contact meter might even show them as hot. There are a few questions about that on this site and others, so if you see a low voltage, research it.

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Either check them for voltage with a multimeter and cap them with wire nuts if there's current or cap them with wire nuts either way for peace of mind.

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